Ballast apparatus for starting and operating electric discharge lamps



. P. EPPERT 3,141,112

July 14, 1964 F BALLAST APPARATUS FOR STARTING AND OPERATING ELECTRIC DISCHARGE LAMPS 2 Sheets-Sheet 1 Filed Aug. 20, 1962 '-II B IO f 23 l 1C2 I} INVENTOR. Franftl/z'z/Pfjo vard 2A7 W ATTORNEY July 14, 1964 F. P. EPPERT 3,141,112

BALLAST APPARATUS FOR STARTING AND OPERATING ELECTRIC DISCHARGE LAMPS Filed Aug. 20, 1962 2 Sheets-Sheet 2 IEJEa E BYZQ Q W ATTORNEY United States Patent 3,141,112 BALLAST APPARATUS FOR STARTING AND OPERATING ELECTRIC DISCHARGE LAMPS Franklin P. Eppert, Danville, Ill., assignor to General Electric Company, a New York corporation Filed Aug. 20, 1962, Ser. No. 217,839 6 Claims. (Cl. 315--231) This invention relates to ballast apparatus for starting and operating electric discharge lamps and more particularly to a ballast apparatus for operating fluorescent lamps from a voltage supply having a voltage greater than the standard 120 volts generally available.

In the design of ballast apparatus or ballasts for operating one or more electric discharge devices, such as fluorescent lamps, from higher voltage sources, as for example, a 480 volt, 60 cycle supply, several problems have been encountered. A commonly used ballast for operation from a 480 volt power supply utilizes a pair of primary windings connected in parallel in either a two magnetic core arrangement or an arrangement employing a single magnetic core. In these conventional arrangements only a part of each of the parallel connected primary windings is included in the lamp circuit. Thus, the operating current in the parts of the primary winding which are included in the lamp circuit is greater than the current in the parts of the primary windings which are excluded from the lamp operating circuit.

It has, therefore, been necessary to wind the parts of the primary winding which are included in the lamp circuit with wire of a larger size than the excluded parts in order to achieve a balance in the heating between the two parts of each of the primary windings. In many cases, the primary copper losses have produced coil operating temperatures which had not been entirely satisfactory. Further, it has not been possible to achieve designs utilizing relatively shorter magnetic core sections wherein the primary copper losses can be minimized. By way of illustration, a conventional 480 volt ballast operating a pair of power groove fluorescent lamps employs a pair of magnetic cores having a combined total length of 19 inches. The comparable 120 volt ballast employs a pair of magnetic cores having a combined total length of 12.254 inches and employs a ballast case having maximum outside dimensions of 2% x 3%; inches and a length of 19 inches. It is, therefore, desirable to provide a ballast for operating fluorescent lamps from higher voltage power supplies, such as a 480 volt supply, which can utilize a magnetic core of relatively shorter length and which, therefore, can utilize a ballast case having the same outside dimensions as the comparable 120 volt ballast. Also, there is a need for such a ballast that can be operated with reduced primary copper losses and that can economically use primary windings having one wire size.

Accordingly, it is a general object of the present invention to provide an improved ballast apparatus for operating one or more fluorescent lamps from a higher voltage source, such as a 480 volt, 60 cycle supply.

It is another object of the present invention to provide an improved ballast apparatus for operating fluorescent lamps wherein the copper losses in the primary windings are minimized.

A further object of my invention is to provide a new and improved ballast apparatus for operating electric discharge lamps from higher voltage sources that can utilize magnetic cores of short length.

Briefly stated, in accordance with one aspect of my invention, I have provided a ballast apparatus for starting and operating one or more electric discharge lamps having a primary divided into four primary parts, a first and 3,141,112 Patented July 14, 1964 ice fourth part of the primary Winding being connected in series circuit relation and the second and third parts of the primary being connected in parallel circuit relation. One end of the first primary part is connected in circuit with one of the input leads of the ballast apparatus and one end of the fourth primary part is connected in circuit with the other input lead. The other end of each of the first and fourth primary parts is connected in circuit with the parallel connected second and third primary parts.

One or more high leakage reactance secondary windings are inductively coupled with at least one of the primary parts and connected in circuit with an output lead. Another output lead is connected in circuit with the parallel connected second and third primary parts so that the voltage across the parallel connected primary parts and the voltage across the high leakage reactance secondary is supplied at the output leads for starting and operating the electric discharge lamp or lamps connected in circuit with the output leads. Preferably, the second and third primary parts are wound with a substantially equal number of turns of conductor wire having substantially the same diameter size as the conductor wire used to wind the first and fourth primary parts.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. My invention, however, both as to organization and mode of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a schematic circuit diagram of a ballast apparatus embodying one form of my invention;

FIGURE 2 is a plan view of the ballast apparatus shown schematically in FIGURE 1 in which the circuit connections have been omitted; I

FIGURE 3 is a schematic circuit diagram of a ballast apparatus in accordance with the invention employing two magnetic cores; and

FIGURE 4 is a schematic diagram of a ballast apparatus of the prior art for operating a pair of fluorescent lamps from a 480 volt alternating power source in which the cathode heating windings and the connection thereto have been omitted.

Referring now to FIGURES 1 and 2 of the drawings, I have illustrated thereina ballast apparatus generally identified by reference numeral 10 and arranged in an enclosure means schematically represented by the dashed rectangle 11. In the illustrated exemplification of the in-' I vention, the ballast apparatus 10 was designed to operate a pair of 96 inch power groove fluorescent lamps L and L2.

The ballast apparatus 10 is comprised of a high reactance transformer 12, a series capacitor C a starting capacitor C output leads 13, 14 for supplying the output of the apparatus 10 to the serially connected lamps L L and the connections 15, 16, 17, 18 to the cathode heating windings H H and H that provide a continuous supply of heating current to the lamp cathodes. The lamps L and L which are fluorescent lamps of the hot cathode type, are preferably positioned in close proximity to a grounded conductive plate or fixture 19 so that the lamps L and L are disposed in capacitive relationship with the grounded fixture to facilitate starting of the lamps L L Since it is generally required that the conductive plate or fixture 19 be grounded, it may be desirable, but not necessary, to place the low potential side of the primary winding in circuit with a suitable ground.

As will be seen in the schematic circuit diagram, the high reactance ballast transformer 12 includes a single magnetic core 20, a primary winding comprised of the primary parts P P P P a secondary winding S, the cathode heating windings H H H magnetic shunts 21, 22 and input terminal leads 23, 24. The input terminal leads 23, 24 are adapted for connection to an alternating power source having a voltage greater than the standard 120 volts generally used. In the exemplification of the invention, the input leads 23, 24 were connected to a 480 volt alternating supply.

It will be noted that connections 26, 27 place the primary parts P and P in parallel circuit relation. One end of each of the primary parts P and P is connected in circuit with one of the input leads 23, 24 and the other end of each of the primary parts P P is connected in circuit with the parallel connected primary parts P P so that primary parts P P are connected in series circuit relation across leads 23, 24. Further, it will be noted that the secondary winding S is connected in circuit with one junction of the parallel connected primary parts P P while the other junction thereof is connected in circuit with output lead 14.

It will be appreciated that a high leakage reactance transformer is normally required in ballasts for operating fluorescent lamps so that the lamp current flow can be properly limited. The lamp current must be limited since electric discharge lamps, such as fluorescent lamps, possess a negative resistance characteristic and would destroy themselves if the current were not regulated. In the ballast transformer 12 as shown in FIGURES 1 and 2, the flux leakage path is formed by the magnetic shunts 21, 22. It will be understood, of course, that a flux leakage path may be formed either through non-magnetic material, such as air, or through magnetic material by forming shunt legs on the yoke members of the magnetic core or by inserting shunts 21, 22 such as are employed in the illustrated embodiment of the invention.

The series capacitor C is connected in series circuit relation with the secondary winding S so that a leading current flows in the lamp circuit during operation thereof. The starting capacitor C is connected in shunt across lamp L so that the lamp L is shunted during the starting condition of the circuit and the open circuit voltage at output leads 13, 14 is initially supplied across lamp L to cause the lamps L L to be sequentially started. As will be seen in the plan view of FIGURE 2, the series capacitor C and the starting capacitor C are included in a two section, three terminal capacitor assembly 30. In the schematic circuit diagram of the FIGURE 1, however, it will be noted that the series capacitor C and the starting capacitor C are schematically shown as two separate capacitors. If desired, a radio interference capacitor may be connected in circuit across the input leads 23, 24 or across the output leads 13, 14 to suppress frequencies fed back from the lamps L and L that may cause radio interference.

Since the fluorescent lamps L and L used in the illustrated exemplification of the invention were of the hot cathode type, it was required that the cathodes of lamps L and L be continuously supplied with a low current during operation to maintain the electron emission of the cathodes. It will be seen that the cathode heating windings H H and H are closely coupled with primary parts P and P Cathode heating windings H and H are connected in circuit with cathodes of lamps L L by output lead 13 and the connections including leads 15, 16 and 17. Cathode heating winding H is connected with a cathode of lamp L by output lead 14 and electrical lead 18.

In FIGURE 1, I have indicated the winding arrangement of the primary parts P P P and P and the secondary winding S by the arrows drawn alongside of the winding. The secondary winding S is wound so that the voltage induced across it is in additive or voltage aiding relation with the voltage applied across the parallel connected primary parts P and P Referring now more specifically to FIGURE 2, I have shown therein the physical arrangement of the ballast apparatus 10 shown schematically in FIGURE 1. The same reference numerals are used to identify the corresponding parts. As shown in FIGURE 2, a coverplate 31 of the ballast case 11 has been partially cut away and the connections of the components and the potting material have been omitted so the arrangement of the components in the case can be more clearly seen.

It will be noted that the ballast transformer 12 is of the shell type. The magnetic core 20 is comprised of a central winding leg 32 on which the coil assemblies 33, 34, 35 are disposed. A pair of outer yoke members 37, 33 are disposed at the sides of the central winding leg 32 and held in assembled relation therewith by clamping elements 39, 40. An insulating member 41 is positioned between the magnetic core 20 and the capacitor assembly 30 to prevent connections to the capacitor terminals from contacting the clamping element 40. It will be seen that the magnetic shunts 21, 22 consists of shunts of magnetic material inserted between the coil assembly 34 and coil assemblies 33, 35.

The coil assemblies 33, 35, which contain the primary parts P P H and P P H H respectively, are dis posed at the ends of the coil assembly 34 containing the secondary winding S. The windings in the coil assemblies 33, 34, 35 are conventionally wound with layers of magnet wire having layers of paper insulation interleaved between the layers of wire.

The apparatus 10 employing the foregoing components Was used to operate a pair of 96 inch power groove lamps from a 60 cycle, 480 volt power source. Of the total voltage, approximately volts was applied across the parallel connected primary parts P and P and about volts was applied across each of the serially connected primary parts P and P For the convenience of those desiring to practice the invention shown in FIGURE 1, the components used in the exemplification of the invention shown in FIGURE 1 are more specifically described as follows:

Primary parts P P 515 turns of .0201 inch in diameter copper wire.

Primary parts P P 377 turns of .0201 inch in diameter copper wire.

Secondary winding S 1516 turns of .0302 inch in diameter copper wire. Cathode heating windings H 12 turns of .0201 inch in H diameter copper wire. Cathode heating winding H 12 turns of .0201 inch in diameter copper wire.

Series capacitor C 6.4 microfarads, 525 volts Starting capacitor C .075 microfarad, 525 volts It was found that the voltages across the primary parts P and P were balanced with the voltage across the primary parts P and P both during the open circuit condition and during the operating condition of the apparatus 10. Further, it was found that this balanced winding arrangement resulted in coil operating temperatures within a total spread of 3 degrees centigrade whereby the primary copper losses were effectively minimized.

Referring now to the schematic circuit diagram shown in FIGURE 1, the operation of the ballast apparatus 10 will now be more fully described. When input terminal leads are connected to a suitable alternating power source, such as a 480 volt, 60 cycle source, the line voltage is proportionally divided across each. of the serially connected primary parts P and P and across the parallel connected primary parts P P A voltage is induced in thesecondary winding S and the cathode heating windings H H and H Initially, the open circuit voltage of the ballast transformer 12 is applied across lamp L since the starting capacitor C in effect causes the voltage to shunt lamp L across which it is connected. Also, there is a small current flow between one of the cathodes of lamp L and the conductive plate 19 so that ionization in the vicinity of a cathode is brought about to aid in the starting of lamp L When lamp L is started, current thereafter flows through lamp L and through the shunting branch which includes the starting capacitor C The flow of current through the starting capacitor C which has a relatively high capacitive reactance provides a voltage drop that is sufiicient to start lamp L When lamp L ignites, its impedance is relatively lower than the reactance of the starting capacitor C and consequently, the current supplied by the ballast transformer flows essentially through the lamps L and L Further, only a negligible amount of current will flow from the lamp cathodes to the conducting fixture 19 because of the high impedance resulting from the capacitive coupling between the lamps L L and the conductive plate 19.

If We take an arbitrary half cycle when the polarity of the voltage applied at input terminal lead 23 is positive with respect to input terminal lead 24, the current takes a path which includes primary part P through the parallel branches, which include the parallel connected primary parts P and P A portion of the line current fiows through the secondary winding S, through the series ca pacitor C output lead 13, lamps L and L output lead 14, and through the primary winding P to input terminal lead 24. It will be noted that during the operating condition of the circuit only the voltage across the parallel connected primary parts P P and the voltage across the secondary windings are supplied at the output leads 13, 14 for operating the serially connected lamps L and L In FIGURE 3, I have illustrated a two-core arrangement embodying another form of my invention. The ballast apparatus is generally identified by the reference numeral 50 and is shown enclosed in a dashed rectangle which schematically represents a ballast case 51 or other enclosure means such as an encapsulant. The ballast apparatus 50 includes a first high reactance transformer 52 having a magnetic core 53, a magnetic shunt 54, primary parts P and P a secondary winding S and cathode heating winding H.;. A second high reactance transformer 55 is provided and has a magnetic core 56, a magnetic shunt 57, primary parts P P a secondary winding S and cathode heating windings H H It will be seen that electrical leads connect primary parts P and P in parallel circuit relationship and that the primary parts P and P are connected in series circuit relation with the parallel connected primary parts P P The secondary windings S S are connected in series circuit relationship by lead 60, secondary winding S being in autotransformer relationship with the primary parts P and P and secondary winding S being in isolated transformer relationship with the primary parts P and P A pair of input terminal leads 62, 63 are provided for the purpose of connecting the ballast apparatus 50 to a suitable alternating power source (not shown) such as a 60 cycle, 480 volt supply.

Primary parts P P P and P were all wound with wire of the same cross-sectional size. The parallel connected primary parts P and P were wound with sufiicient turns as compared with primary parts P P so that during operation 110 volts of the supply voltage appeared across primary parts P P As will be seen in FIGURE 3, lamps L and L are positioned in close proximity to a conductive plate 64 so that the lamps L and L are disposed in capacitive relationship with the conductive plate 64. Ballast transformers 52, 55 are connected in circuit with the serially connected lamps L L by output leads 65, 66. Essentially, the output of the ballast apparatus 50 is supplied to the lamps L L at the two output leads 65; 66. Cathode heating winding H is connected in circuit with the lamp L by output lead 65 and electrical leads 67, 68 and 6 is inductively coupled with the primary parts P and P Cathode heating windings H and H are inductively coupled with primary winding parts P and P and are connected in circuit with cathodes of lamps L and L by output lead 66 and leads 69, 70, 71.

It will be also seen that a series capacitor C is connected in series circuit with the serially connected secondary windings S and S and introduces in the lamp circuit suificient capacitive reactance as compared with the inductive reactance of the transformers 52, 55 so that a leading current flows through the secondary windings S S during operation. A starting capacitor C connected across leads 65, 69 is provided so that the starting voltage is first applied across lamp L Since the primary parts P P and P P and the secondary windings S and S respectively, are disposed in a side by side relation on the magnetic cores 53, 56, there is a certain amount of leakage reactance in the magnetic circuit because of this arrangement. As shown in FIG- URE 3, additional leakage reactance is introduced in each of the ballast transformers 52, 55 by providing high reluctance flux leakage paths or the magnetic shunts 54 and 57. It will be understood that depending upon the design of the particular transformer, flux leakage paths may be formed either through non-magnetic material, such as air, or through magnetic material by the provision of shunt legs integrally formed with the yoke sections or by means of insertable magnetic shunts 54, 57 as were employed in the illustrated embodiment of my invention.

By Way of a specific exemplification of the invention, a ballast apparatus 50, as shown in FIGURE 3, was constructed for starting and operating a pair of 96 inch power groove fluorescent lamps. The ballast apparatus 50 utilized the following components which are set forth by way of illustration:

Primary parts P P Cathode heating windings H H 12 turns of .0201 inch in diameter wire. Cathode heating winding H 13 turns of .0201 inch in diameter wire. Series capacitor C 6.3 microfarads, 540 volts A.C.

Starting capacitor C .075 microfarad, 540 volts A.C.

In order to demonstrate the advantages of the present invention over a conventional ballast, operating data was obtained for the apparatus 50 shown in FIGURE 3 and a comparable conventional ballast such as I have illustrated in FIGURE 4. In the conventional ballast 80, it will be seen that primary parts P P P and P are connected in parallel across a pair of input terminal leads 81, 82. The cathode heating windings and the connections for these windings are omitted in the schematic circuit diagram of FIGURE 4. Secondary windings S and 5.; are serially connected and inductively coupled with the primary parts P P and P P on magnetic cores 83, 84 of ballast transformers 85 and 86, respectively. Additional leakage reactance in the magnetic circuits of transformers 85, 86 is provided by the magnetic shunts 87, 88. A series capacitor C is used to provide a net capacitive reactance in the lamp circuit and a starting capacitor is used to sequentially start lamps L and L The output of the ballast 80 is supplied to the serially connected lamps L L by output leads 89, 90.

The conventional ballast 80 tested was designed to operate a pair of 96 inch power groove lamps from a 60 cycle, 480 volt power source. Primary parts P and P 7 Were wound with a magnet wire having a diameter of .0126 of an inch, and primary parts P and P were wound with a magnet wire having a diameter of .0201 of an inch. All of the primary parts P P P and P of the ballast 50 were wound with a magnet wire having a diameter of .0201 of an inch.

It was found that the primary copper losses in the ballast 50 incorporating the improved winding arrangement of the invention were significantly reduced. For example, the copper losses in the primary parts P and P of the conventional ballast 80 were found to be 8.7 watts as compared to 6.8 watts for the primary parts P and P of the ballast St). The total copper losses in the primaries of the conventional ballast 80 were found to be 20.2 watts as compared with 16.4 watts for the improved ballast 50. Further, it was found that fewer turns could be used in the primary winding of the improved arrangement. The total number of primary turns used in the transformers 52, 55 was 1784 turns as compared with 2814 turns in the conventional ballast 80 shown in FIGURE 4. Consequently, less window space was required for the coils and the magnetic cores 53 and 56 were shorter in length, 6.127 inches as compared with 9.500 inches for magnetic cores 83 and 84 of the conventional ballast 8t) with equivalent copper losses. In addition, the insulation requirements for the coils of the ballast 50 were reduced since each primary coil in the improved ballast 59 was in effect a 300 volts coil.

While the present invention has been described by reference to specific exemplifications thereof, it is to be understood that modifications may be made by those skilled in the art without actually departing from the invention. It is, therefore, intended in the appended claims to cover all such equivalent variations that fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A ballast apparatus for operating electric discharge lamps from an alternating power source comprising: a voltage transforming means including at least one magnetic core, a pair of input leads for connection with the alternating power source, a first, a second, a third and a fourth primary part, said first and fourth primary parts being connected in circuit with the input leads and said second and third primary parts being connected in parrallel circuit relation with each other, said parallel connected second and third primary parts being connected in series circuit relation with said first and fourth primary parts, at least one high leakage reactance secondary winding inductively coupled with at least a pair of said primary parts, one junction of said parallel connected second and third primary parts being connected in circuit with one end of said secondary winding and circuit means for supplying the output of the apparatus to said electric discharge lamps and including output leads for connection with said lamps, one of said output leads being connected in circuit with the other end of said secondary winding and the other of said output leads being connected in circuit with the other junction of said parallel connected second and third primary parts.

2. A ballast apparatus for operating at least on electric discharge lamp from an alternating power source comprising: a voltage transforming means including at least one magnetic core, a high reactance secondary winding and a primary comprised of a first, a second, a third and a fourth primary part, a pair of input leads for connec tion with the alternating power source, said high reactance secondary winding being inductively coupled with at least one of said primary parts, one end of said first primary part being connected in circuit with one of said input leads, and one end of said fourth primary part being connected in circuit with the other of said input leads, means connecting said second and third primary parts in parallel circuit relation, the other end of each of said first and fourth primary parts being connected in circuit with the parallel connected second and third primary parts, said high reactance secondary winding being connected in circuit with said parallel connected second and third primary parts, and circuit means for supplying the output of the apparatus to said at least one electric discharge lamp, said circuit means including output leads for connection in circuit with said lamp, one of said output leads being connected in circuit with the other end of said high reactance secondary winding and the other of said output leads being connected in circuit with said parallel connected second and third primary parts.

3. A ballast apparatus for operating a pair of fluorescent lamps from an alternating power source comprising: a voltage transforming means including a magnetic core, a primary and a high reactance secondary winding, said primary including a first, second, third and fourth primary part, a pair of input leads for connection with the power source, and circuit means for supplying the output of the apparatus to said fluorescent lamps, said circuit means including a starting capacitor and connections for placing said starting capacitor in shunt with one of said fluorescent lamps and including output leads for connection with said fluorescent lamps, one end of said first primary part being connected in circuit with one of said input leads and one end of said fourth primary part being connected in circuit with the other of said input leads, said second and third primary parts being connected in parallel circuit relation, said parallel connected second and third primary parts being connected at one junction thereof with the other end of said first primary part and with said high reactance secondary winding and being connected at the other junction thereof in circuit with the other end of said fourth primary part and one of the output leads, and said second and third primary parts being wound with substantially the same number of turns and all of said primary parts being wound with a conductor wire of the same size.

4. A ballast apparatus for operating a pair of fluorescent lamps from an alternating power source comprising: a ballast transformer having a primary and a secondary winding inductively coupled therewith on a magnetic core, said primary being comprised of a first, second, third and fourth pirmary part, a pair of input leads for connection in circuit with the alternating current source, said second and third primary parts being connected in parallel circuit relation with each other and having one junction thereof connected in circuit with said secondary winding, said first and fourth primary parts being connected in series circuit relation with said parallel connected second and third primary parts across said input leads, a series capacitor connected in series circuit relation with said secondary winding, and circuit means including a starting capacitor and electrical connections for placing said starting capacitor in shunt with one of said lamps and including output leads for supplying the output of the apparatus to said lamps, one of said output leads being connected in circuit with said serially connected capacitor and secondary winding and the other of said output leads being connected with said parallel connected second and third primary parts, and said second and third primary parts being wound with a substantially equal number of turns of conductor wire having substantially the same diameter size as the first and fourth primary parts.

5. A ballast apparatus for operating at least one fluorescent lamp from a high voltage power source comprising: a pair of input leads for connection with the power source, a ballast transformer having a primary Winding and a secondary winding inductively coupled therewith on a magnetic core, said primary winding being comprised of a first, second, third and fourth primary part, said second and third primary parts being connected in parallel circuit relation, said first and fourth primary parts being connected in series circuit relation with said parallel connected second and third primary parts across said input leads, said secondary winding being connected with said parallel connected second and third primary parts and being wound and arranged so that said voltage induced across said secondary winding is in voltage aiding relation with the voltage across said parallel connected sec- 0nd and third primary parts, and circuit means including output leads for connection in circuit with said fluorescent lamp, one of said output leads being connected in circuit with said secondary Winding and the other of said output leads being connected in circuit with said secondary winding and the other of said output leads being connected in circuit with said parallel connected second and third primary parts, and said second and third primary parts being wound of a substantially equal number of turns of wire of the same diameter size as said first and fourth primary parts.

6. A ballast apparatus for operating a plurality of fluorescent lamps from an alternating power source comprising: a first transformer including a first magnetic core, a first high leakage reactance secondary winding and a first and second primary part inductively coupled with said first high leakage reactance secondary winding on said first magnetic core, a second transformer including a second magnetic core, a second secondary winding, a third and fourth primary part inductively coupled with said secondary winding on said second magnetic core, a pair of input leads for connection in circuit with said alternating power source, one end of said first primary part being connected in circuit with one of said input leads, and one end of said fourth primary part being connected in circuit with the other of said input leads, said second and third primary parts being connected in parallel circuit relation with each other and in series circuit relation with said first and fourth primary parts, and circuit means connecting said first and second secondary winding in series circuit relationship and in circuit with one junction of said parallel connected second and third primary parts, said circuit means including output leads for connection with said fluorescent lamps and for supplying the output of the apparatus thereto, one of the output leads being connected in circuit with the other junction of said parallel connected second and third primary parts and the other of said output leads being connected in circuit with said secondary winding, and said second and third primary parts being comprised of substantially the same number of turns and being wound with a conductor wire having the same diameter size as the conductor wire of said first and fourth primary parts.

References Cited in the file of this patent UNITED STATES PATENTS 3,040,208 Feinberg June 19, 1962 FOREIGN PATENTS 54,268 France Feb. 9, 1949 

1. A BALLAST APPARATUS FOR OPERATING ELECTRIC DISCHARGE LAMPS FROM AN ALTERNATING POWER SOURCE COMPRISING: A VOLTAGE TRANSFORMING MEANS INCLUDING AT LEAST ONE MAGNETIC CORE, A PAIR OF INPUT LEADS FOR CONNECTION WITH THE ALTERNATING POWER SOURCE, A FIRST, A SECOND, A THIRD AND A FOURTH PRIMARY PART, SAID FIRST AND FOURTH PRIMARY PARTS BEING CONNECTED IN CIRCUIT WITH THE INPUT LEADS AND SAID SECOND AND THIRD PRIMARY PARTS BEING CONNECTED IN PARALLEL CIRCUIT RELATION WITH EACH OTHER, SAID PARALLEL CONNECTED SECOND AND THIRD PRIMARY PARTS BEING CONNECTED IN SERIES CIRCUIT RELATION WITH SAID FIRST AND FOURTH PRIMARY PARTS, AT LEAST ONE HIGH LEAKAGE REACTANCE SECONDARY WINDING INDUCTIVELY COUPLED WITH AT LEAST A PAIR OF SAID PRIMARY PARTS, ONE JUNCTION OF SAID PARALLEL CONNECTED SECOND AND THIRD PRIMARY PARTS BEING CONNECTED IN CIRCUIT WITH ONE END OF SAID SECONDARY WINDING AND CIRCUIT MEANS FOR SUPPLYING THE OUTPUT OF THE APPARATUS TO SAID ELECTRIC DISCHARGE LAMPS AND INCLUDING OUTPUT LEADS FOR CONNECTION WITH SAID LAMPS, ONE OF SAID OUTPUT LEADS BEING CONNECTED IN CIRCUIT WITH THE OTHER END OF SAID SECONDARY WINDING AND THE OTHER OF SAID OUTPUT LEADS BEING CONNECTED IN CIRCUIT WITH THE OTHER JUNCTION OF SAID PARALLEL CONNECTED SECOND AND THIRD PRIMARY PARTS. 